Aluminum Alloy And Brazing Sheet Manufactured Therefrom

ABSTRACT

An aluminum alloy for heat exchanger applications includes Al and unavoidable impurities, Mg in an amount from about 0.05 wt. % to about 0.40 wt. %, Cr in an amount from about 0.02 wt. % to about 0.50 wt. %, Zr in an amount from about 0.01 wt. % to about 0.35 wt. %, Ti in an amount from about 0.01 wt. % to about 0.25 wt. %, Si in an amount of less than about 0.15 wt. %, Cu in an amount from about 0.25 wt. % to about 0.8 wt. %, and Mn in an amount from about 1.0 wt. % to about 1.7 wt. %.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of co-pending International Application No. PCT/US2005/009841, filed on Mar. 23, 2005, which claims the benefit of U.S. Provisional Application Nos. 60/614,490, filed Oct. 1, 2004, 60/614,489, filed Oct. 1, 2004, 60/614,483, filed Oct. 1, 2004, 60/617,161, filed Oct. 12, 2004, and 60/646,985, filed Jan. 27, 2005; a continuation-in-part application of co-pending International Application No. PCT/US2005/034706, filed Sep. 28, 2005, which claims the benefit of U.S. Provisional Application Nos. 60/614,496, filed Oct. 1, 2004, 60/617,666, filed Oct. 13, 2004, and 60/627,085, filed Nov. 12, 2004; a continuation-in-part application of co-pending International Application No. PCT/US2005/034707, filed Sep. 28, 2005, which claims the benefit of U.S. Provisional Application Nos. 60/614,490, filed Oct. 1, 2004, 60/614,489, filed Oct. 1, 2004, 60/614,483, filed Oct. 1, 2004, 60/617,161, filed Oct. 12, 2004; 60/646,985, filed Jan. 27, 2005, and PCT/US2005/009841, filed Mar. 23, 2005; and a continuation-in-part application of co-pending International Application No. PCT/US2005/040626, filed Nov. 9, 2005, which claims the benefit of U.S. Provisional Application No. 60/627,085, filed Nov. 12, 2004, all of which this application claims the benefit, and which applications are incorporated herein by reference and made a part hereof.

TECHNICAL FIELD

The invention relates generally to aluminum alloys for brazing sheet applications, and more particularly to aluminum alloy brazing sheet materials having increased strength and creep resistance.

BACKGROUND OF THE INVENTION

Aluminum brazing sheet is widely used to manufacture various heat exchangers such as radiators, charge air coolers, evaporators, and condensers in the automotive industry. One of the much-needed improvements in the automotive industry is the overall weight reduction in order to enhance fuel economy. The goal of weight reduction extends to all components of a vehicle including heat exchangers. Accordingly, research and development efforts are continuing to down-gage the tube stock in automotive radiators, while increasing strength and erosion/corrosion resistance.

The present alloy and brazing sheet material are provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior alloys and brazing sheets of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings.

SUMMARY OF THE INVENTION

The present disclosure provides an aluminum alloy for heat exchanger applications includes Al and unavoidable impurities, Mg in an amount from about 0.05 wt. % to about 0.40 wt. %, Cr in an amount from about 0.02 wt. % to about 0.50 wt. %, Zr in an amount from about 0.01 wt. % to about 0.35 wt. %, Ti in an amount from about 0.01 wt. % to about 0.25 wt. %, Si in an amount of less than about 0.15 wt. %, Cu in an amount from about 0.25 wt. % to about 0.8 wt. %, and Mn in an amount from about 1.0 wt. % to about 1.7 wt. %.

According to one aspect, the alloy contains Mg in an amount from about 0.1 wt. % to about 0.35 wt. %, Cr in an amount from about 0.05 wt. % to about 0.25 wt. %, Zr in an amount from about 0.05 wt. % to about 0.25 wt. %, and Ti in an amount from about 0.05 wt. % to about 0.2 wt. %.

According to another aspect, the alloy contains Mg in an amount of about 0.257 wt. %, Cr in an amount of about 0.139 wt. %, Zr in an amount of about 0.144 wt. %, and Ti in an amount of about 0.147 wt. %.

According to another aspect, the alloy contains Fe in an amount of less than about 0.30 wt. %, and Zn in an amount of less than about 0.1 wt. %.

According to another aspect, the alloy contains Cu in an amount from about 0.5 wt. % to about 0.8 wt. %, and Mn in an amount from about 1.2 wt. % to about 1.7 wt. %.

The disclosure also provides an aluminum alloy brazing sheet material including a core alloy and a clad alloy. The core alloy is an aluminum alloy as described above.

According to one aspect, the material has a room temperature post-braze yield strength of at least 78 MPa.

According to another aspect, the material has an average creep rate of less than 1×10⁻⁸/sec. at 260° C., under a stress of 6.0 Ksi.

According to another aspect, the material has an average creep rate of less than 5×10⁻⁸/sec. at 260° C., under a stress of 6.0 Ksi.

According to another aspect, the material has an average creep rate of less than 1×10⁻⁷/sec. at 260° C., under a stress of 6.0 Ksi.

The disclosure further provides an aluminum alloy brazing sheet material including a core alloy and a clad alloy. The core alloy is an aluminum alloy that includes Al and unavoidable impurities, Mg in an amount from about 0.40 wt. % to about 0.80 wt. %, Cr in an amount from about 0.02 wt. % to about 0.50 wt. %, Zr in an amount from about 0.01 wt. % to about 0.35 wt. %, Ti in an amount from about 0.01 wt. % to about 0.25 wt. %, Si in an amount of less than about 0.15 wt. %, Cu in an amount from about 0.25 wt. % to about 0.8 wt. %, and Mn in an amount from about 1.0 wt. % to about 1.7 wt. %.

According to one aspect, the material has a room temperature post-braze yield strength of at least 94 MPa.

According to another aspect, the material has an average creep rate of less than 5×10⁻⁷/sec. at 250° C., under a stress of 6.0 Ksi.

Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

To understand the present invention, it will now be described by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a graph depicting creep data of three different alloys, at the temperatures and stress levels indicated therein; and

FIG. 2 is a graph depicting creep data of five different alloys, at 260° C. and a stress level of 6 Ksi.

DETAILED DESCRIPTION

While this invention is susceptible of embodiments in many different forms, there are shown in the drawings and will herein be described in detail certain exemplary embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated.

Aluminum alloys are disclosed herein for use as heat exchanger materials, which include the addition of several alloying elements. These aluminum alloys can be used in a brazing sheet material for use in a heat exchanger. Such brazing sheet materials are often composites containing a core layer, along with at least one clad layer. The core layer is generally made of a core alloy material that provides strength and structural support. The brazing sheet may have one or two brazing clad layers, typically having a lower melting point. One embodiment of such a brazing clad layer is an Al—Si alloy, such as 4045 alloy or another 4000 series Al alloy. In some embodiments, the brazing sheet may also have an interior clad or interior liner layer to provide increased corrosion resistance. This can be important in tubing applications, as the interior liner layer would contact the fluid flowing through the tubing. One example of an interior liner layer is disclosed in U.S. Pat. No. 6,667,115, which is incorporated by reference herein. Another example of such an interior clad layer is a 7xxx series Al alloy. It is understood that in some embodiments, the disclosed materials may be used without any interior cladding.

In one exemplary embodiment, the Al alloy includes at least the following alloying elements: magnesium (Mg), chromium (Cr), zirconium (Zr), and titanium (Ti). As described below, the inventors have found that the use of Mg, Cr, Zr, and Ti together as alloying elements combine to create a synergistic effect that imparts greater strength, including greater post-braze yield strength, as well as much greater creep resistance, than would be otherwise expected. In some embodiments, the alloy may also contain one or more of silicon (Si), iron (Fe), copper (Cu), manganese (Mn), and Zinc (Zn). In further embodiments, the alloy may contain additional elements, either by impurity or addition, including, for example, vanadium (V). Any of the alloying elements discussed herein may be added to the alloy or may be present as an impurity, or both.

Magnesium (Mg): Mg is an effective element for improving the strength of the core alloy. In one embodiment, the alloy contains Mg in an amount from about 0.05 wt. % to about 0.40 wt. %. Alloys having Mg compositions of about 0.40 wt. % or less are useful in controlled atmosphere brazing (CAB), which can be done using a flux material. Alloys having Mg compositions greater than about 0.40 wt. % may sometimes present difficulties in CAB applications. In another embodiment, the alloy contains Mg in an amount from about 0.10 wt. % to about 0.35 wt. %. In another embodiment, disclosed in Example 1 below, the alloy contains Mg in an amount of about 0.257 wt. %.

Chromium (Cr): Additions of Cr enhance the strength of the alloy, as well as its corrosion resistance. In one embodiment, the alloy contains Cr in an amount from about 0.02 wt. % to about 0.50 wt. %. In another embodiment, the alloy contains Cr in an amount from about 0.05 wt. % to about 0.25 wt. %. In another embodiment, disclosed in Example 1 below, the alloy contains Cr in an amount of about 0.139 wt. %.

Zirconium (Zr: Additions of Zr enhance the strength of the alloy, as well as its corrosion resistance. In one embodiment, the alloy contains Zr in an amount from about 0.01 wt. % to about 0.35 wt. %. In another embodiment, the alloy contains Zr in an amount from about 0.05 wt. % to about 0.25 wt. %. In another embodiment, disclosed in Example 1 below, the alloy contains Zr in an amount of about 0.144 wt. %.

Titanium (Ti): Ti can act as a dispersoid, and additions of Ti enhance the strength of the alloy, as well as its corrosion resistance. In one embodiment, the alloy contains Ti in an amount from about 0.01 wt. % to about 0.25 wt. %. In another embodiment, the alloy contains Ti in an amount from about 0.05 wt. % to about 0.20 wt. %. In another embodiment, disclosed in Example 1 below, the alloy contains Ti in an amount of about 0.147 wt. %.

Other elements may be added to the alloy or present as impurities in significant amounts, including Si, Cu, Fe, Mn, and Zn. In some embodiments, V may be added as well.

Silicon (Si): Si is sometimes used to improve the strength of an Al alloy. However, in some embodiments of the alloy disclosed herein, the Si content is relatively low to improve corrosion resistance. The lower silicon content allows formation of a “brown band” of manganese precipitates during brazing, which corrodes preferentially to improve corrosion resistance of the core alloy. In one embodiment, the alloy contains Si in an amount less than about 0.15 wt. %.

Copper (Cu): Cu can be used to improve the strength of the alloy, as well as corrosion resistance. In one embodiment, the alloy contains Cu in an amount from about 0.25 wt. % to about 0.80 wt. %. In another embodiment, the alloy contains Cu in an amount from about 0.50 wt. % to about 0.80 wt. %.

Manganese (Mn): Mn can be used to improve the strength of the alloy, as well as its corrosion resistance. In one embodiment, the alloy contains Mn in an amount from about 1.0 wt. % to about 1.7 wt. %. In another embodiment, the alloy contains Mn in an amount from about 1.20 wt. % to about 1.70 wt. %.

Iron (Fe): Fe is nearly always present as an impurity in Al alloys, and excessive Fe content can decrease corrosion resistance. In some embodiments of the alloy disclosed herein, the Fe content is relatively low. In one embodiment, the alloy contains Fe in an amount less than about 0.30 wt. %. Additionally, the desirable limits of Fe content and Mn content of the alloy are interrelated. If the combined amount of Fe and Mn is too high, undesirable intermetallics may form. Thus, if the Mn content is within the upper disclosed ranges, it is desirable to have Fe content significantly lower than the disclosed upper limit.

Zinc (Zn): Zn is often an impurity in Al alloys, and additions of Zn can improve the corrosion resistance of an alloy. In one embodiment, no Zn is added to the alloy, and Zn content is kept to an impurity level, which may be 0.1% or less.

Vanadium (V): V can be used to improve strength in the alloy. In one embodiment, the alloy contains V in an amount from about 0.05 wt. % to about 0.30 wt. %. In another embodiment, the alloy contains V in an amount from about 0.10 wt. % to about 0.25 wt. %.

In an alternate embodiment, the alloy contains higher levels of Mg than in the embodiments those described above. In one embodiment, the alloy contains Mg in an amount from about 0.40 wt. % to about 0.80 wt. %. In another embodiment, disclosed in the example below, the alloy contains Mg in an amount of about 0.55 wt. %. Alloys containing higher Mg levels are useful in vacuum furnace brazing techniques. In such techniques, the higher Mg content allows the Mg to consume oxygen in the vacuum brazing atmosphere so that use of a flux is not necessary. In these higher-Mg embodiments, the compositions of Cr, Zr, Ti, Si, Cu, Mn, Fe, Zn, and V may be within the ranges described above for the lower-Mg embodiments.

The alloy embodiments described above provide increased strength and creep resistance, among other benefits, as compared to other Al-based heat exchanger alloys. The inventors have discovered that the use of Mg, along with Cr, Zr, and Ti, produces a synergistic effect to impart this greater strength to the alloy, when included in the amounts described above. The alloy also retains strength for significantly longer time periods at elevated temperatures. This strength retention not only improves creep resistance, but also ensures that yield strength will not drop to unacceptable levels during use, as many uses of the disclosed alloy involve elevated temperature applications. The exact mechanism or reason for the synergistic effect is not known. However, the benefits created are greater than would be expected through use of less than all of the four elements. In particular, the alloy provides a superior combination of post-braze yield strength, elongation, strength retention, and creep resistance, as compared to other alloys.

The creep resistance of the alloy varies with the amount of Mg, Cr, Ti, and Zr included therein, within the ranges listed above. However, it is contemplated that including Mg, Cr, Ti, and Zr in any of the ranges listed above will provide enhanced creep resistance at elevated temperatures. In one embodiment, the alloy, when used as a core of a brazing sheet, provides an average creep rate of less than 5.0×10⁻⁷/sec. at 260° C. at a stress of 6 Ksi. In another embodiment, the alloy, when used as a core of a brazing sheet, provides an average creep rate of less than 1.0×10⁻⁷/sec. at 260° C. at a stress of 6 Ksi. In another embodiment, the alloy, when used as a core of a brazing sheet, provides an average creep rate of less than 5.0×10⁻⁸/sec. at 260° C. at a stress of 6 Ksi. In another embodiment, the alloy, when used as a core of a brazing sheet, provides an average creep rate of less than 1.0×10⁻⁸/sec. at 260° C. at a stress of 6 Ksi.

The strength of the alloy also varies with the amount of alloying additions. However, it is contemplated that including Mg, Cr, Ti, and Zr in any of the ranges listed above will provide enhanced creep resistance at room temperature and elevated temperatures. In one embodiment, the alloy provides a room temperature post-braze yield stress of at least 94 MPa. In another embodiment, the alloy provides a room temperature post-braze yield stress of at least 83 MPa. In another embodiment, the alloy provides a room temperature post-braze yield stress of at least 78 MPa.

The increased strength and creep resistance, and the effects of alloying additions, are illustrated by way of example below.

EXAMPLE 1

Three alloys were prepared, identified as K320 (an existing alloy), K331, and K3D. The compositions for these three alloys are listed in Table 1 below. The alloy K3D includes a Mg composition within the range of about 0.05 wt. % to about 0.40 wt. %, as described above with respect to the lower-Mg embodiments. The alloy K331 includes a Mg composition within the range of about 0.40 wt. % to about 0.80 wt. %, as described above with respect to the higher-Mg embodiments. TABLE 1 Core alloy chemistries (wt %) Element K320 K331 K3D Si 0.07 0.08 0.07 Fe 0.19 0.21 0.17 Cu 0.52 0.50 0.70 Mn 1.05 1.62 1.45 Mg 0.25 0.55 0.257 Cr — 0.11 0.139 Zn 0.02 0.03 — Ti 0.02 0.036 0.147 Zr — — 0.144

Each of these alloys was used as a core alloy in forming a composite braze sheet, with a single braze clad layer of 4045 Al alloy, each sheet having approximately the same dimensions and layer thicknesses as the other sheets. The alloys were manufactured from ingots with appropriate alloying additions, and these ingots were machined suitably for clad application. Composite samples consisting of a core alloy and a braze clad (10-15% of total thickness) were assembled and roll-bonded by hot rolling, then processed to a final gauge by appropriate combinations of cold rolling and annealing steps. The resulting braze sheets were tested for room temperature pre-braze yield strength, ultimate tensile strength, and elongation, room temperature post-braze yield strength, ultimate tensile strength, and elongation, and creep rate at elevated temperatures. The pre- and post-braze tensile properties are listed in Table 2 below. The creep rate data and testing temperatures are summarized in Table 3 below. FIG. 1 illustrates the creep rate of all three alloys at 250-260° C. TABLE 2 Pre-braze and post-braze tensile properties Braze YS, UTS, Core alloy condition Ksi (MPa) Ksi (MPa) % Elongation K320 Pre-braze — — — Post-braze  8.45 (58.3) 23.45 (161.7) 16.5 K331 Pre-braze 14.27 (98.4) 27.57 (190.1) 16.3 Post-braze 13.66 (94.2) 30.35 (209.2) 12.2 K3D Pre-braze 31.11 (214.5) 35.21 (242.8)  8.4 Post-braze 11.42 (78.8) 25.91 (178.6) 15.8

TABLE 3 Creep rate summary of K320, K331 and K3D core braze sheets Material T ° C. Stress, Ksi Average creep rate (/Sec) K320 core 260 6.2  1.8E−06 250 6.0  7.8E−07 8.0  1.8E−05 K331 core 250 5.0 1.61E−08 6.0 2.10E−07 7.0 1.87E−06 8.0 1.83E−06 9.0 3.19E−05 200 8.0 1.20E−08 9.0 1.00E−08 10.0 4.44E−08 K3D core 260 6.0 8.30E−09 246 7.0 4.21E−09

As illustrated in Table 2, the K3D alloy, which contained Mg, Cr, Zr, and Ti in amounts within the ranges described above for the alloy, provided significant increases in post-braze yield strength and tensile strength, with little change in elongation, as compared to K320, which included smaller amounts of Cr, Zr, and Ti. As illustrated in Table 3 and FIG. 1, the K3D alloy exhibited vastly improved creep resistance at elevated temperatures, in the range of orders of magnitude, as compared to the K320 and K331 alloys. In fact, as shown in FIG. 1, the K3D alloy even exhibited significantly higher creep resistance at 10° C. higher temperatures than the other alloys. The K331 alloy exhibited significantly higher post-braze yield strength, particularly when compared to K320. The K331 alloy also exhibited similar creep resistance compared to K320.

EXAMPLE 2

Two existing base alloys were prepared, referred to as CA43 and K328. Three new alloys were also prepared based on modifications of the K328 alloy, adding Mg, Cu, Ti, Cr, Zr, and V (in some examples), listed as K328-M1, K328-M2, and K328-M3. The compositions are listed below in Table 4. In preparing the M1 sample, the following nominal compositions were added to the K328 alloy: +0.15 wt. % Mg, +0.1 wt. % Cu, +0.1 wt. % Ti, +0.15 wt. % Cr, and +0.15 wt. % Zr. In preparing the M2 sample, the following compositions were added to the K328 alloy: +0.15 wt. % Mg, +0.1 wt. % Cu, +0.15 wt. % Ti, +0.15 wt. % Cr, +0.15 wt. % Zr, and +0.15 wt. % V. In preparing the M3 sample, the following compositions were added to the K328 alloy: +0.15 wt. % Mg, +0.25 wt. % Cu, +0.25 wt. % Ti, +0.25 wt. % Cr, +0.25 wt. % Zr, and +0.25 wt. % V. TABLE 4 Core alloy chemistries (wt. %) Element CA43 K328 K328-M1 K328-M2 K328-M3 Si 0.08 0.07 0.07 0.07 0.07 Fe 0.20 0.17 0.17 0.17 0.17 Cu 0.50 0.50 0.70 0.691 0.645 Mn 1.05 1.45 1.45 1.45 1.45 Mg 0.25 0.09 0.257 0.222 0.233 Cr — — 0.139 0.130 0.202 Zr — — 0.144 0.165 0.287 Ti 0.02 0.03 0.147 0.161 0.247 V — — — 0.139 0.262

Each of these alloys was used as a core alloy in forming a composite braze sheet, with a single braze clad layer of 4045 Al alloy, each sheet having approximately the same dimensions and layer thicknesses as the other sheets. The alloys were manufactured from ingots with appropriate alloying additions, and these ingots were machined suitably for clad application. Composite samples consisting of a core alloy and a braze clad (10-15% of total thickness) were assembled and roll-bonded by hot rolling, then processed to a final gauge by appropriate combinations of cold rolling and annealing steps. The samples were clad in a single braze clad layer of a common 4xxx series alloy with 10% nominal Si. The resulting braze sheets were tested for room temperature pre-braze yield strength, ultimate tensile strength, and elongation, room temperature post-braze yield strength, ultimate tensile strength, and elongation, and creep rate at elevated temperatures. The pre- and post-braze tensile properties are listed in Table 5 below. The creep rate data and testing temperatures are summarized in Table 6 below. FIG. 2 illustrates the creep rate of all five alloys at 260° C., with a load stress of 6 Ksi. TABLE 5 Pre-braze and post-braze tensile properties Core Braze UTS, Alloy condition YS, Ksi (MPa) Ksi (MPa) % Elongation CA43 Pre-braze — — — Post-braze 8.45 (58.3) 23.45 (161.7) 16.5 K328 Pre-braze 27.83 (191.9) 31.74 (218.9) 10.8 Post-braze 10.35 (71.3)  23.35 (161.0) 13.2 K328-M1 Pre-braze 31.11 (214.5) 35.21 (242.8) 8.4 Post-braze 11.42 (78.8)  25.91 (178.6) 15.8 K328-M2 Pre-braze 32.95 (227.2) 36.80 (253.7) 6.0 Post-braze 12.10 (83.4)  24.90 (171.7) 16.6 K328-M3 Pre-braze 34.12 (235.3) 37.84 (260.9) 4.5 Post-braze 11.29 (77.9)  25.87 (178.4) 13.3

TABLE 6 Creep rate summary Steady state Average creep rate Creep rupture time Material creep rate (/Sec) (/Sec) (hrs) CA43 2.92E−07 1.14E−06 29 K328 1.78E−06 2.52E−06 13 K328-M1 2.67E−08 4.05E−08 144 K328-M2 7.71E−08 2.21E−07 148 K328-M3 3.40E−08 1.34E−07 244

As evidenced by the figures in Table 5, the addition of Mg, Cr, Zr, and Ti increased the post-braze yield strength and ultimate tensile strength of the alloy. In addition, as shown in Table 6 and FIG. 2, these additions vastly improved the creep rate and creep rupture time of the alloys, by orders of magnitude. The addition of V did not appear to result in substantially improved properties.

Accordingly, as illustrated by Example 2, the properties of many Al alloys can be improved through a method including addition of alloying elements. An Al alloy composition is provided, and Mg, Cr, Ti, and Zr are added thereto. In one embodiment, the method includes adding up to about 0.30 wt. % Mg. In another embodiment, the method includes adding up to about 0.15 wt. % Mg. In one embodiment, the method includes adding up to about 0.1 wt. % Cu. In one embodiment, the method includes adding up to about 0.25 wt. % Ti. In another embodiment, the method includes adding up to about 0.10 wt. % Ti. In one embodiment, the method includes adding up to about 0.10 wt. % Cr. In another embodiment, the method includes adding up to about 0.15 wt. % Cr. In a further embodiment, the method includes adding up to about 0.25 wt. % Cr. In one embodiment, the method includes adding up to about 0.10 wt. % Zr. In another embodiment, the method includes adding up to about 0.15 wt. % Zr. In a further embodiment, the method includes adding up to about 0.25 wt. % Zr. The methods may also include the addition of other alloying elements, including up to about 0.25 wt. % V. This method can be practiced with many standard Al alloys, including those of the 1xxx, 3xxx, and 5xxx series and similar alloys.

Various improvements in materials for brazing sheet applications are disclosed herein, especially with reference to heat exchanger materials are presented herein. As disclosed herein, heat exchanger materials can be utilized in applications such as radiators, charge air coolers, condensers, evaporators, and the like, including use in tubes for such applications, without limitation. The disclosed alloys provide improved post-braze strength and creep resistance compared to previous alloys, at both room temperature and normal heat exchanger tube operating temperatures, due at least in part to the synergistic effect of the addition of the disclosed concentrations of Mg, Cr, Zr, and Ti. Ultimate Tensile Strength (UTS), Yield Strength (YS) and Elongation (E) of alloys as disclosed herein were determined according to ASTM B557-94.

Several alternative embodiments and examples have been described and illustrated herein. A person of ordinary skill in the art would appreciate the features of the individual embodiments, and the possible combinations and variations of the components. A person of ordinary skill in the art would further appreciate that any of the embodiments could be provided in any combination with the other embodiments disclosed herein. It is understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. Accordingly, while the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention and the scope of protection is only limited by the scope of the accompanying claims. 

1. An aluminum alloy for heat exchanger applications, comprising: Al and unavoidable impurities; Mg in an amount from about 0.05 wt. % to about 0.40 wt. %; Cr in an amount from about 0.02 wt. % to about 0.50 wt. %; Zr in an amount from about 0.01 wt. % to about 0.35 wt. %; Ti in an amount from about 0.01 wt. % to about 0.25 wt. %; Si in an amount of less than about 0.15 wt. %; Cu in an amount from about 0.25 wt. % to about 0.8 wt. %; and Mn in an amount from about 1.0 wt. % to about 1.7 wt. %.
 2. The aluminum alloy of claim 1, further comprising: Mg in an amount from about 0.1 wt. % to about 0.35 wt. %; Cr in an amount from about 0.05 wt. % to about 0.25 wt. %; Zr in an amount from about 0.05 wt. % to about 0.25 wt. %; and Ti in an amount from about 0.05 wt. % to about 0.2 wt. %.
 3. The aluminum alloy of claim 2, further comprising: Mg in an amount of about 0.257 wt. %; Cr in an amount of about 0.139 wt. %; Zr in an amount of about 0.144 wt. %; and Ti in an amount of about 0.147 wt. %.
 4. The aluminum alloy of claim 1, further comprising: Fe in an amount of less than about 0.30 wt. %; and Zn in an amount of less than about 0.1 wt. %.
 5. The aluminum alloy of claim 1, further comprising: Cu in an amount from about 0.5 wt. % to about 0.8 wt. %; and Mn in an amount from about 1.2 wt. % to about 1.7 wt. %.
 6. An aluminum alloy brazing sheet material comprising a core alloy and a clad alloy, the core alloy comprising: Al and unavoidable impurities; Mg in an amount from about 0.05 wt. % to about 0.40 wt. %; Cr in an amount from about 0.02 wt. % to about 0.50 wt. %; Zr in an amount from about 0.01 wt. % to about 0.35 wt. %; Ti in an amount from about 0.01 wt. % to about 0.25 wt. %; Si in an amount of less than about 0.15 wt. %; Cu in an amount from about 0.25 wt. % to about 0.8 wt. %; and Mn in an amount from about 1.0 wt. % to about 1.7 wt. %.
 7. The brazing sheet material of claim 6, wherein the core alloy further comprises: Mg in an amount from about 0.1 wt. % to about 0.35 wt. %; Cr in an amount from about 0.05 wt. % to about 0.25 wt. %; Zr in an amount from about 0.05 wt. % to about 0.25 wt. %; and Ti in an amount from about 0.05 wt. % to about 0.2 wt. %.
 8. The brazing sheet material of claim 7, wherein the core alloy further comprises: Mg in an amount of about 0.257 wt. %; Cr in an amount of about 0.139 wt. %; Zr in an amount of about 0.144 wt. %; and Ti in an amount of about 0.147 wt. %.
 9. The brazing sheet material of claim 6, wherein the core alloy further comprises: Fe in an amount of less than about 0.30 wt. %; and Zn in an amount of less than about 0.1 wt. %.
 10. The brazing sheet material of claim 6, wherein the core alloy further comprises: Cu in an amount from about 0.5 wt. % to about 0.8 wt. %; and Mn in an amount from about 1.2 wt. % to about 1.7 wt. %.
 11. The brazing sheet material of claim 6, wherein the material has a room temperature post-braze yield strength of at least 78 MPa.
 12. The brazing sheet material of claim 6, wherein the material has an average creep rate of less than 1×10⁻⁸/sec. at 260° C. under a stress of 6.0 Ksi.
 13. The brazing sheet material of claim 6, wherein the material has an average creep rate of less than 5×10⁻⁸/sec. at 260° C., under a stress of 6.0 Ksi.
 14. The brazing sheet material of claim 6, wherein the material has an average creep rate of less than 1×10⁻⁷/sec. at 260° C., under a stress of 6.0 Ksi.
 15. An aluminum alloy brazing sheet material comprising a core alloy and a clad alloy, the core alloy comprising: Al and unavoidable impurities; Mg in an amount from about 0.40 wt. % to about 0.80 wt. %; Cr in an amount from about 0.02 wt. % to about 0.50 wt. %; Zr in an amount from about 0.01 wt. % to about 0.35 wt. %; Ti in an amount from about 0.01 wt. % to about 0.25 wt. %; Si in an amount of less than about 0.15 wt. %; Cu in an amount from about 0.25 wt. % to about 0.8 wt. %; and Mn in an amount from about 1.0 wt. % to about 1.7 wt. %.
 16. The brazing sheet material of claim 15, wherein the core alloy further comprises: Cr in an amount from about 0.05 wt. % to about 0.25 wt. %; Zr in an amount from about 0.05 wt. % to about 0.25 wt. %; and Ti in an amount from about 0.05 wt. % to about 0.2 wt. %.
 17. The brazing sheet material of claim 15, wherein the core alloy further comprises: Fe in an amount of less than about 0.30 wt. %; and Zn in an amount of less than about 0.1 wt. %.
 18. The brazing sheet material of claim 15, wherein the core alloy further comprises: Cu in an amount from about 0.5 wt. % to about 0.8 wt. %; and Mn in an amount from about 1.2 wt. % to about 1.7 wt. %.
 19. The brazing sheet material of claim 15, wherein the sheet has a room temperature post-braze yield strength of at least 94 MPa.
 20. The brazing sheet material of claim 15, wherein the material has an average creep rate of less than 5×10⁻⁷/sec. at 250° C., under a stress of 6.0 Ksi. 